package com.xtaller.core.helper;

/**
 * Created by Administrator on 2017/5/27.
 * 全局唯一id生成器
 */
public class IdHelper {
    private Long workerId;
    private Long datacenterId;
    private Long sequence = 0L;
    private Long twepoch = 459407593L;
    private Long workerIdBits = 5L; //节点ID长度
    private Long datacenterIdBits = 5L; //数据中心ID长度
    private Long maxWorkerId = -1L ^ (-1L << workerIdBits); //最大支持机器节点数0~31，一共32个
    private Long maxDatacenterId = -1L ^ (-1L << datacenterIdBits); //最大支持数据中心节点数0~31，一共32个
    private Long sequenceBits = 12L; //序列号12位
    private Long workerIdShift = sequenceBits; //机器节点左移12位
    private Long datacenterIdShift = sequenceBits + workerIdBits; //数据中心节点左移17位
    private Long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits; //时间毫秒数左移22位
    private Long sequenceMask = -1L ^ (-1L << sequenceBits); //4095
    private Long lastTimestamp = -1L;

    private static class IdGenHolder {
        private static final IdHelper instance = new IdHelper();
    }

    public static IdHelper getInstance(){
        return IdGenHolder.instance;
    }

    public IdHelper() {
        this(0L, 0L);
    }

    public IdHelper(long workerId, long datacenterId) {
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
        }
        this.workerId = workerId;
        this.datacenterId = datacenterId;
    }

    public synchronized long nextId() {
        long timestamp = timeGen(); //获取当前毫秒数
        //如果服务器时间有问题(时钟后退) 报错。
        if (timestamp < lastTimestamp) {
            throw new RuntimeException(String.format(
                    "Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }
        //如果上次生成时间和当前时间相同,在同一毫秒内
        if (lastTimestamp == timestamp) {
            //sequence自增，因为sequence只有12bit，所以和sequenceMask相与一下，去掉高位
            sequence = (sequence + 1) & sequenceMask;
            //判断是否溢出,也就是每毫秒内超过4095，当为4096时，与sequenceMask相与，sequence就等于0
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp); //自旋等待到下一毫秒
            }
        } else {
            sequence = 0L; //如果和上次生成时间不同,重置sequence，就是下一毫秒开始，sequence计数重新从0开始累加
        }
        lastTimestamp = timestamp;
        // 最后按照规则拼出ID。
        // 000000000000000000000000000000000000000000  00000            00000       000000000000
        // time                                                               datacenterId   workerId    sequence
        long id = ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift)
                | (workerId << workerIdShift) | sequence;

        return id + 1000000000000000000L;
    }

    protected long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    protected long timeGen() {
        return System.currentTimeMillis();
    }


    /**
     * 常规id生成
     * */
    public static String getId(){
        String id = getInstance().nextId()+"";
        //String ym = TimeHelper.formatNow("yyMMdd");
        String ym = TimeHelper.formatNow("yyMM");
        id = id.substring(4,19);
        return ym+id;
    }
    /**
     * 根据业务id生成id
     * */
    public static String getId(int businessId){
        String id = getInstance().nextId()+"";
//        String dd = TimeHelper.formatNow("dd");
//        String ym = TimeHelper.formatNow("yyMM");
        id = id.substring(3,19);
        return businessId+id;
    }

    /**
     * 生成多个id
     * @param len 生成的数量
     * */
    public static long[] getIds(int len){
        long[] ids = new long[len];
        String ym = TimeHelper.formatNow("yyMMddHH");
        for(int i=0;i<len;i++){
            String id = getInstance().nextId()+"";
            id = id.substring(4,20);
            ids[i] = Long.parseLong(ym+id);
        }
        return ids;
    }

    /**
     * 生成多个id
     * @param len 生成的数量
     * @param businessId 业务编码
     * */
    public static long[] getIds(int len,int businessId){
        long[] ids = new long[len];
        String ym = TimeHelper.formatNow("yyMMdd");
        for(int i=0;i<len;i++){
            String id = getInstance().nextId()+"";
            id = id.substring(4,19);
            ids[i] = Long.parseLong(businessId+id);
        }
        return ids;
    }
    public static void main(String[] args){
        System.out.println("======================");
        for(int i=1;i<99;i++){
            System.out.println(getId(101));
            System.out.println(getId(101));
            System.out.println(getId(101));
            System.out.println(getId(101));
            System.out.println(getId(101));
            System.out.println(getId(101));
            System.out.println(getId(101));
        }
        System.out.println(getId());
    }
}
